Natural Weathering Studies of Polypropylene

Polypropylene (PP) has achieved a dominating position and hence, their consumption increases thereby littering, which lead to environmental pollution. Photodegradation seems to be a better choice because of naturally available sunlight as energy source for degradation. The present work involves the study of the variation of degradation behavior of PP film during tropical summer and winter seasons. The photodegradation is followed by Fourier transform infrared (FTIR) spectroscopic technique. Various indices like hydroxyl, carbonyl, vinylidene, lactones, ester, carboxylic acid and crystallinity are calculated and these values increased after a brief induction period. The variation in the mechanical properties like tensile strength and elongation at break percentages are determined. The scanning electron microscopic (SEM) images of weathered PP showed surface cracks when carbonyl index value increases sharply and the mechanical properties show a sudden decrease. Attempted life time prediction using mathematical models showed that the carbonyl growth is more affected by ultraviolet (UV) and cumulative total solar radiation for PP weathered during summer. The loss in tensile strength of PP weathered during summer is more dependent on the average temperature and the UV portion of the total solar radiation whereas, intensity of UV radiation has profound effect on the tensile strength of PP weathered during winter.     

Collective work and resilience of complex systems

This article aims to describe the characteristics of collective working situations in complex systems – especially those in nuclear power plants – related to common forms of cooperation, in order to improve systems resilience. In addition, we will try to detail some aspects of collective working situations, emphasizing the differences between various forms of control. The similarities between work activities (multi-addressed messages, linkage to regulation, central and peripheral information) are nonetheless exposed. We conclude by proposing a contribution to support systems design, thus facilitating cooperation in teamwork activities.     

A study on the arsenic concentration in groundwater of a coastal aquifer in south-east India: an integrated approach

The occurrence of arsenic in drinking water and its detrimental effects have drawn much attention in recent years. Several studies have been conducted in the deltaic plains of River Ganga, NE part of the India, and in other countries, but no systematic study was conducted in South India on occurrence of arsenic in groundwater. The main aim of this study is to determine the level of arsenic in groundwater and to understand the relation with other geochemical parameters of groundwater in the south-eastern coastal aquifer at Kalpakkam region, India. This region is represented by three different lithologies, viz. charnockites, flood plain alluvium and marine alluvium. Twenty-nine representative samples of groundwater were collected and analysed for major ions, metals and isotopes such as ²H and ¹⁸O. In addition, geophysical method was also attempted to understand the subsurface condition. The spatial variation in arsenic (As) indicates that higher concentration was observed around the landfill sites and irrigated regions, which was supported by geochemical, statistical and isotopic inferences. The variation in the As with depth, lithology and sources has been clearly brought out. Though the values of As does not exceed the drinking water permissible limit (10 mg/l), it has reached a near permissible level of 8.7 ppb. Hence, it is essential to understand the geochemical behaviour of As for a proper future management of the water resource in the study area.     

Dynamic trends of heavy metal contents in plants and soil under different industrial air pollution regimes

Based on 30-year monitoring of Ni²⁺ and Cu²⁺ concentrations in the organic horizon of Albic Rustic Podzols and the foliage of six plant species, a dynamic trend in the level of heavy metal accumulation in the components of forest ecosystems of the Kola Peninsula has been revealed against the background of five- to eightfold reduction of pollutant emissions. The direction of the trend has been found to differ: the size of polluted area and pollution level increase with time, while the concentrations of heavy metals in plants decrease due to reduction in their input from the polluted air.     

Influence of experimental conditions on manifestation of the group effect in the gypsy moth, <Emphasis Type="Italic">Lymantria dispar</Emphasis> L.

The effect of rearing conditions for gypsy moth larvae on parameters of their development (its duration and mortality) was studied in experiments with early instar larvae reared singly or in groups. The manifestation of the group effect was analyzed depending on the choice of experimental unit (the larva or the rearing container) and the amount of volume per larva. The observed effects were evaluated quantitatively.     

Siberian musk deer in the diets of tiger and bears in the Sikhote-Alin

The role of the Siberian musk deer in the diets of the Amur tiger, brown bear, and Asian black bear has been studied in the Sikhote-Alin State Biosphere Reserve in 1992 to 2016. Information has been collected from 763 tiger feeding sites, and the contents of tiger feces have been analyzed. Radiotelemetry has been used to evaluate tiger–musk deer relationships. The musk deer accounted for 0.26% of all animal species found to be eaten by the tiger. Musk deer remains in feces of the tiger, brown bear, and Asian black bear occurred with frequencies of 1.3, 0.2, and 0.3%, respectively. A case of musk deer avoiding the presence of brown bear is described.